Role of main neuroendocrine pathways activated by swim stress on mast cell-dependent peritoneal TNF production after LPS administration in mice.

OBJECTIVE AND DESIGN: To characterize the effects of swim stress on the early mast cell (MC)-dependent peritoneal production of TNF in response to lipopolysaccharide (LPS) administration in mice, identifying the neuroendocrine mediators involved. SUBJECTS: Ten to twelve-week-old Swiss Webster, C57BL/6 J or c-Kit (Wsh/Wsh) mice were used. TREATMENT: Animals were intraperitoneally challenged with LPS at different times after forced swimming (FS) and peak TNF production was determined in peritoneal washes at optimal time after LPS administration. Selective blockage of main neuroendocrine pathways was performed before swim stress. METHODS: TNF concentrations were determined by ELISA. RESULTS: FS provoked an immediate and transient inhibition of LPS-elicited, MC-dependent TNF accumulation in peritoneum, which lasted around 30 min. Suppresive effects of FS were absent on MC-deficient c-Kit (Wsh/Wsh) mice but were recovered after reconstitution with MC. Adrenalectomy or DSP4 administration increased basal ip TNF levels and enhanced LPS-induced TNF release without any effect on stress-induced inhibitory effects, mifepristone did not produce any change on stress-induced inhibition, whereas mecamylamine administration increased basals and attenuated stress effects. CONCLUSIONS: Swim stress transiently inhibits the canonical MC-dependent response of TNF production in response to LPS in murine peritoneal cavity with the main participation of the cholinergic anti-inflammatory reflex.

Central tegmental field and sexual behavior in the male rat: effects of neurotoxic lesions.

The medial preoptic area/anterior hypothalamus (MPOA/AH) is a key structure in the control of male sexual behavior. This area has reciprocal connections with mesencephalic and brainstem structures including the central tegmental field (CTF). It has been suggested that the CTF receives somatosensory information generated in the genitals promoting activation of the MPOA/AH. In the present study we evaluated the effects of bilateral neurotoxic lesions of the CTF upon male rat sexual behavior. We also explored the effects of these lesions on sociosexual behaviors, partner preference, sexual incentive motivation and motor execution. Tests were performed before and after bilateral quinolinic acid infusions. The lesion was evaluated by quantifying neuronal nuclei (Neu-N) and by the presence of glial fibrillary acidic protein (GFAP) immunohistochemistries. A significant reduction in the percentage of animals displaying mounts, intromissions, and ejaculations was observed in the bilateral and misplaced lesion groups 1 week after the lesion. In the second week post-lesion, only animals with bilateral damage of the CTF showed a significant reduction in sexual behavior. In the third post-lesion test, the percentage of animals displaying sexual behavior returned to control levels. The frequency of pursuit and self-grooming was reduced, and genital exploration was increased after the lesion. Partner preference and sexual incentive motivation were not affected by the lesion suggesting that the CTF is not involved in the appetitive aspects of sexual behavior. Mount, intromission, and ejaculation latency were increased in animals with damage of the CTF and in animals with lesions outside this region. Motor execution was also affected in both groups, suggesting that alterations in latencies could be associated with damage not specific to the CTF.

The role of the dorsolateral tegmentum in the control of male sexual behavior: a reevaluation.

The medial preoptic area/anterior hypothalamus (MPOA/AH) plays a key role in the control of male sexual behavior. Independently of the type, MPOA/AH lesions permanently eliminate male sexual behavior in the rat. The MPOA/AH projects among other structures to the dorsolateral tegmentum (DLT). Bilateral electrolytic lesions of the DLT or the unilateral electrolytic destruction of the MPOA/HA combined with a contralateral electrolytic lesion of the DLT eliminate male sexual behavior. In the present experiment, we evaluated if neurotoxic lesions of the DLT produce the same behavioral deficits as those observed after electrolytic lesions. This would allow us to evaluate if neurons of the DLT or the fibers passing through this area are important in the control of male sexual behavior. To this aim, sexually experience male rats were tested for socio-sexual behavior, partner preference and motor execution in order to determine if the possible behavioral changes could be attributed to alterations in sexual motivation or motor execution. One week after the bilateral DLT lesions the animals were evaluated in the same behavioral tests. The lesions were identified by glial fibrillary acidic protein (GFAP) and neuronal nuclear protein (Neu-N) immunohistochemistry. No significant consistent effects upon sexual behavior were observed in any of the groups, including the group with clear bilateral damage of the DLT. A reduction in the percentage of males displaying ejaculation in the first post-lesion test was observed for all groups injected with quinolinic acid. No effects upon partner preference or motor coordination were observed after the lesion in any of the groups. The lack of effect of DLT neurotoxic lesions upon mating suggests that neurons of this structure are not involved in the control of male sexual behavior.